Flame-resistant fiber board



United States Patent FLAME-RESISTANT FIBER BOARD Anthony J. Page andDavid R. P. Haig, Somerville, N. J., assiguors to .l'ohns-ManvilleCorporation, New York, N. Y., a corporation of New York No Drawing.Application November 1, 1952, Serial No. 318,335

13 Claims. (Cl. 117-69) This invention relates to cellulosic fiber boardand more particularly to cellulosic fiber insulating board having aflame-resistant, finished surface.

The commercial product commonly referred to as fiber insulating board ismanufactured from wood, cane or other vegetable fiber by a pulp feltingor molding process, and usually contains a suitable sizing materialincorporated in the product to render it water-resistant. Such fiberinsulating boards are conventionally utilized as structural buildingboard, lath, sheathing, roof insulation board, and interior wall panels.composition of the fibers consolidated to form the insulating board,such a product has a serious disadvantage as a construction material inthat the board is flammable, and, unless treated, it fails to provide adesirable barrier to the rapid propagation of flame through a buildingutilizing such structural elements.

Various proposals have been made to render fiber insulating boardflame-resistant. It has been proposed to incorporate variousconventional flameproofing compositions within the board or in thedecorative coating normally applied to the board, particularly one usedfor an interior wall surface. Many of these proposals have resulted in afiber insulating board having somewhat more flame-resistance than anuntreated board. However, these proposals have not generally resulted ininsulating boards of sufi'icient flame-resistant characteristics to meetvarious governmental and industrial standards.

Recorded voluntary standards of the trade for structural fiberinsulating board are set forth in the United States Department ofCommerce Commercial Standard CS-42-49. In order to meet the requirementsof 08-42-49 for a Flame-resistant Classification, the char area,according to the above standard, should be no more than 12 squareinches, and flaming, glow or smoldering should not continue more than 60seconds after the fuel is exhausted. In order to insure that such aproduct also meets the Slow Burning Classification set forth in theUnited States Government Federal Specification SS-A-118a, E-3c, however,it is preferred that the specimen exhibit a char area no greater thanapproximately 9 square inches under the test conditions set forth in theabove-entitled standards.

Conventional fiber insulating board without fiame proofing treatment andwithout a decorative coating such as a conventional casein paint, whentested under standard conditions, exhibits a char area of about 58square inches and exhibits smoldering after the 60 sec- Due to theorganic "ice Accordingly, it is anobject of this invention to provide aflame-resistant cellulosic fiber board which will serve as an efiicientbarrier to rapid propagation of flame.

Another object of the invention is to provide a flameresistantinsulating board meeting the standards prescribed in various commercialand governmental standards such as Department of Commerce CommercialStandard CS-42-49 and United States Government Federal SpecificationSS.A l18a, E-3c, and hence exhibiting a .char area of no more than 12square inches and not supporting combustion 60 seconds after an ignitingflame is extinguished.

It is a further object of this invention to provide a flame-proofinsulating board which is flexible and which can be flexed withoutdestroying its flameproof characteristics.

It is an additional and more specific object of this -in'- vention toprovide a cellulosic fiber board which has been treated on at least oneside to render it flameproof and which has applied thereto a uniform,decorative coating.

With the above and other objects and features in view, the inventionconsists in the improved flame-resistant cellulosic fiber boardhereinafter described and more particularly defined in the appendedclaims.

The fiber board preferably employed in accordance with this invention isa light weight felted or molded web of cellulosic fibers such as wood,cane or other vegetable fibers, and, preferably, has incorporatedtherein conventional additives, such as a sizing material which renders.the board relatively water-resistant. In order to render such a webflameproof, the formed board is coated with a substantial amount of acoating containingspecific types of mineral ingredients, which coatingis applied as an initial primer coat when a decorative paint top coat isapplied to the insulating board.

The coating utilized in this invention to lend the insulating board itsflame-resistant characteristics essentially comprises either a syntheticor a natural mixture of from approximately to by weight of anon-swelling clay mineral and from approximately 5 to 25% of a swellableclay mineral of fine particle size. Exemplary of such non-swelling claysare moderate particle size clays of the kaolinite group such askaolinite, endellite, etc.; clays of the micaceous clay group such asillite, attapulgite, etc.; and other equivalent clay minerals. Exemplaryof the swellable natural minerals of fine particles .size are swellingcolloidal clay minerals which can expand along the C crystalaxis withoutaltering the other two major crystal axes (A or B), such asmontmorillinite or bentonite, hectorite, beidellite, etc. The syntheticor natural mixture of the above-mentioned materials in the indicatedproportions should also have the physical characteristic of an averagebonding modulus of at least approximately 200 lbs/sq. in. as determinedby standard test conditions outlined in the Report f the Committee onStandards, The American Ceramic Society, Year Book 1921-1922.

As heretofore indicated, the coating composition may comprise asynthetic mixture of such minerals in the indicated range of proportionsor may comprise a natural mixture of such minerals. Exemplary of such anatural mineral mixture and the preferred essential mineral forfabricating a flamerresistant fiber board in accordance with thisinvention is a natural ball clay mined at Cren- Shaw, Mississippi, andknown as Mississippi M & D clay. This clay essentially comprises amixture of kaolini'te and montmorillinite, has a bonding modulus ofabout approximately 210 lbs./ sq. in., and leaves upon ignition alignitish residue. When used herein, the expression a clay having theclay characteristics of Mississippi M '& D clay is intended to define aclay which has the same chemical and physical properties as MississippiM & D clay regardless of the location where mined or the vendor thereof.

A fiber insulating board may be rendered flame-resistant in accordancewith this invention by coating the board with an aqueous dispersion ofthe above-entitled synthetic or natural mineral mixture alone, in amountsufficient to deposit at least 14 lbs. of clay per 1000 sq. ft. of boardsurface. The maximum amount of such a mineral mixture which may beutilized is limited only by the amount capable of being dispersed in thedesired vehicle to a workable coating consistency, and, in turn, theamount of dispersion applied to the board. In normal practice the amountof aqueous dispersion applied when utilizing such a natural or syntheticmineral mixture alone will not exceed that required to deposit 30 lbs.of clay mineral solids per 1000 sq. ft. of insulating board surface.

While an insulating board can be rendered flame-resistant to a degreesufficient to exhibit a char area of less than 9 square inches byemploying the synthetic or natural mineral mixture alone, variousingredients may be, and preferably are, added to the coating to improvethe appearance and characteristics of the finally obtained product. Theprime additive preferably utilized in conjunction with a natural mineralclay mixture such as M & D clay, is a light colored clay having highviscosity reduction when treated with a defiocculating agent, forexample, a kaolin such as Tako or ball clay such as Cooley. An additiveclay having such properties is utilized in conjunction with the naturalclay mixture in order to enable the formation of a relatively highsolids concentration dispersion for ease in application of substantialamounts of the essential mineral mixture utilized in accordance withthis invention. The additive clay should have a relatively light colorwhich will serve to provide as light colored flameproofing clay primercoat as possible, obviously desirable when conventional finishes such aslight colored casein paints are utilized as decorative top coatings.Since the additive clay is a substantially inorganic material, it isnon-flammable and will also serve, in some degree, to render theinsulating board flame-resistant. The additive clay in itself, however,will not render the board flame-resistant to a sufficient degree, andactual test measurements have indicated that a clay such as Tako, foundsuitable for this invention as an additive and as a non-swelling mineralof moderate particle size, when used alone does not diminish the chararea below 12 square inches.

When an additive clay, such as Tako clay, is utilized in conjunctionwith the natural clay mixture, such as Mississippi M & D clay, theamount of clay dispersion utilized should be sufficient to deposit atleast 14, and preferably -25, lbs. of clay solids per 1000 sq. ft. ofboard surface. Again, the maximum solids content which may be depositedis dependent only upon the amount of solids capable of being dispersedto a workable viscosity, and the total amount of clay solids depositedwill not generally exceed 40 lbs. per 1000 sq. ft. of board surface.When using such a clay dispersion, the natural clay mixture of theabove-entitled characteristics should be present in amount sufficient todeposit at least 10, and preferably 11-13, lbs. of its clay solids aloneper 1000 sq. ft. of board surface treated, and in the optimumcompositions equal amounts of additive clay and the natural clay mixtureare used.

Additional ingredients may be utilized in the primer coating, ifdesired. For example, a bonding agent, such as starch, may be added tothe clay dispersion to increase the adhesion of the clay particles tothe base fiber board, in amounts which in the preferred coatingcompositions may be sufficient to deposit up to 1 lb. of starch per 1000sq. ft. of board surface. Small amounts of pigmenting and fungicidalingredients may also be added to the coating for their conventionalpurposes, if desired.

As heretofore indicated, the coating utilized according to thisinvention serves a dual function in the formation of decorative surfacedstructural fiber board products. Primarily, the coating serves to rendera fiber insulating board flame-resistant and, in particular,sufficiently flame-resistant to meet the requirements set forth invarious commercial standards such as Department of Commerce StandardsCS-42-49 and the United States Government Federal SpecificationsSS-A-1l8a, E-3c. T he flatneproofing clay coating also serves as anexcellent primer for conventional decorative paints utilized in themanufacture of insulating board products, such as a pigmented caseinpaint. The flameproofing coating of this invention strongly adheres tothe fibers of the insulating board and forms a good sealant for thedecorative top coating. The coating is sufficiently flexible to allowthe insulating board to be flexed without cracking the fiameproofingcoating and, in turn, the decorative top coating. The flameproofingcoating also has the important characteristic of being capable ofapplication without causing warpage of the board to which it is appliedduring the manufacturing procedure.

The following are examples of various flame-resistant cellulosic fiberboards and their general method of preparation. It is understood, ofcourse, that the particular compositions and methods recited areexemplary and are not to be considered to limit the invention to theparticular compositions and proportions outlined. All percentagesindicated in the examples are by weight.

Example I A /z" thick cellulosic fiber, wet felted insulating boardhaving a density of approximately 15-18 lbs./cu. ft. was coated with twofelts of a slurry having an approximate composition of:

Percent Starch 1.5 M & D ball clay 24.0 Tako kaolin 24.0 Clay dispersingagent 0.3 Anti-mildew agent 0.2

Water 50.0

The slurry was coated on the board in amount sufficient to deposit atotal of approximately 25 lbs. of mineral solids per 1000 sq. ft. oftreated surface. The coated board was then painted with four felts of aconventional casein paint in amount suificient to deposit approximately18 lbs. of paint solids per 1000 sq. ft. The adhesion of the primingmineral slurry to the treated board, and of the decorative coating tothe prime coating was excellent, and no cracking of the finish appeared.When tested in accordance with Commercial Standards 42-49, the boardexhibited a char area of only 8.3 square inches and exhibited nosmoldering or afterglow.

Example II Percent Starch 1.0 Peerless coating clay -Q 34.0 Bentonite5.0 Dispersing agent 0.2 Anti-mildew agent 0.2

Water 59.6

The coating exhibited no cracking and, as in Example I, the adhesion ofthe coatings to the board and to each other was excellent. When testedin accordance with Commercial Standards 42-49, the insulating boardexhibited no smoldering and a char area of approximately 8.8 squareinches.

In addition to flameproofing the normal front surface of an insulatingboard in the manner herein disclosed, it is also desirable to utilizethe coating composition of this invention as a fiarneproofing coating onthe back surface of such a product. Since in many instances the backsurface of the board might be subjected to igniting flame as in a withinthe walls fire, the use of a coating of the formulas herein disclosed onboth surfaces of an insulating board renders the board sufiicientlyflameresistant to prevent the rapid propagation of flame, regardless ofwhich surface is exposed to the igniting flame. Actual test results offiber insulating board coated on both sides with the clay coating ofthis invention have indicated no flame spread on the front or backsurface of the board even after exposure to an igniting fiame for aperiod of time sufficient to burn through the board.

While the invention has been particularly defined with regard to fiberinsulating board, it is obvious that the invention has applicability tothe treatment of any structural body formed essentially from flammablefibers. For example, a wood fiber hardboard or the like may be treatedin accordance with this invention in order to render it moreflame-resistant.

It will be understood that the details given herein are for the purposeof illustration, not restriction, and that variations within the spiritof the invention are intended to be included in the scope of theappended claims.

What we claim is:

1. A flame-resistant structural panel comprising a web of cellulosicfibers having at least one major surface coated with a coatingcomprising a mixture of approximately 75 to 95% of a non-swelling clayselected from the group consisting of clays of the kaolinite group andthe micaceous group and from approximately 5 to 25% of a swellable clayof fine particle size selected from the group consisting of clays of themontmorillonite group, in amount sufiicient to deposit at leastapproximately lbs. of clay solids per 1000 square feet of web surfacetreated.

2. A flame-resistant structural panel comprising a web of cellulosicfibers having at least one major surface coated with a coatingcomprising a mixture of approximately 75 to 95 of a non-swelling clayselected from the group consisting of clays of the kaolinite group andthe micaceous group and from aproximately 5 to 25% of a swellable clayof fine particle size selected from the group consisting of clays of themontmorillonite group, having a bonding modulus of at leastapproximately 200 lbs. per square inch, in amount suificient to depositat least approximately 10 lbs. of clay solids per 1000 square feet ofweb surface treated.

3. A flame-resistant structural panel comprising a web of cellulosicfibers having at least one major surface coated with a coatingcomprising a clay having the clay characteristics of Mississippi M & Dclay, in amount sufficient to deposit at least approximately 10 lbs. ofclay solids per 1000 square feet of web surface treated.

4-. A flame-resistant structural panel comprising a web of cellulosicfibers having at least one major surface coated with a coatingcomprising a mixture of approximately 75 to 95% of a kaolinite clay andfrom approximately 5 to 25 of a montmorillinite clay, in amountsufiicient to deposit at least approximately 14 lbs. of clay solids per1000 square feet of web surface treated.

5. A flame-resistant structural panel comprising a web of cellulosicfibers having at least one major surface coated with a coatingcomprising a mixture of approximately 75 to 95% of a non-swelling clayselected from the group consisting of clays of the kaolinite group andthe micaceous group and from approximately 5 to 25% of a swellable clayof fine particle size selected from the group consisting of clays of themontmorillonite group, together with a clay having high viscosityreduction when treated with a defiocculating agent selected from thegroup consisting of kaolin clays and ball clays, in amount sutficient todeposit at least approximately 14 lbs. of clay solids per 1000 squarefeet of web surface treated, said mixture comprising at least 10 lbs. ofthe clay solids of said total coating.

6. A flame-resistant structural panel comprising a web of cellulosicfibers having at least one major surface coated with a coatingcomprising a mixture of approximately 75 to of a non-swelling clayselected from the group consisting of clays of the kaolinite group andthe micaceous group and from approximately 5 to 25% of a swellable clayof fine particle size selected from the group consisting of clays of themontmorillonite group, having a bonding modulus of approximately 200lbs. per square inch, together with a clay having high viscosityreduction when treated with a deflocculating agent selected from thegroup consisting of kaolin clays and ball clays, in amount sufiicient todeposit at least approximately 14 lbs. of clay solids per 1000 squarefeet of web surface treated, said mixture comprising at leastapproximately 10 lbs. of the clay solids of said total coating.

7. A flame-resistant structural panel comprising a web of cellulosicfibers having at least one major surface coated with a coatingcomprising a clay having the clay characteristics of Mississippi M & Dclay and a clay having high viscosity reduction when treated with adeflocculating agent selected from the group consisting of kaolin claysand ball clays, in amount sufiicient to deposit at least approximately14 lbs. of clay solids per 1000 square feet of web surface treated, saidmixture comprising at least approximately 10 lbs. of the clay solids ofsaid total coating.

8. A flame-resistant structural panel comprising a fiber insulatingboard having at least one major surface coated with a coating comprisinga clay having the clay characteristics of Mississippi M & D clay and akaolinite clay, in amount sufficient to deposit at least approximately10 lbs. of solids of said first clay per 1000 square feet of surfacetreated, and to deposit a total of at least approximately 14 lbs. ofclay solids per 1000 square feet of surface coated.

9. A flame-resistant structural panel comprising a fiber insulatingboard having at least one major surface coated with a coating comprisinga clay having the clay characteristics of Mississippi M & D clay and asubstantially equal amount of a kaolinite clay, in amount suificient todeposit at least approximately 10 lbs. of solids of said first clay per1000 square feet of surface treated, and to deposit a total of at leastapproximately 14 lbs. of clay solids per 1000 square feet of surfacecoated.

10. A flame-resistant, decorative finished structural panel comprising afiber insulating board having at least one major surface coated with apriming coating comprising a clay having the clay characteristics ofMississippi M & D clay, in amount sufficient to deposit at leastapproximately 10 lbs. of clay solids per 1000 square feet of surfacetreated, and a decorative paint coating superimposed on said primingcoating.

11. A flame-resistant structural panel comprising a fiber insulatingboard having both the front and back major surfaces coated with acoating comprising a mixture of approximately 75-95% of a non-swellingclay selected from the group consisting of clays of the kaolinite groupand the micaceous group and from approximately 525% of a swellable clayof fine particle size selected from the group consisting of clays of themontmorillonite group, in amount sufiicient to deposit at leastapproximately 10 lbs. of clay solids per 1000 square feet of web surfacetreated.

12. A flame-resistant structural panel comprising a fiber insulatingboard having both the front and back major surfaces coated with acoating com rising a clay having the clay characteristics of MississippiM & D clay, in amount sufficient to deposit at least approximately 10lbs. of clay solids per 1000 square feet of surface treated.

13. A flame-resistant structural panel comprising a fiber insulatingboard having both the front and back major surfaces coated with acoating comprising a clay having the clay characteristics of MississippiM & D clay and a substantially equal amount of a kaolinite clay, inamount sufficient to deposit at least approximately 10 lbs. of saidfirst clay solids per 1000 square feet of surface treated, and todeposit a total of at least approximately 14 lbs. of clay solids per1000 square feet of surface coated.

References Cited in the file of this patent UNITED STATES PATENTSSchwartz June 29, 1943 Schwartz June 29, 1943 OTHER REFERENCES

1.
 10. A FLAME-RESISTANT, DECORATIVE FINISHED STRUCTURAL PANEL COMPRISING A FIBER INSULATING BOARD HAVING AT LEAST ONE MAJOR SURFACE COATED WITH A PRIMING COATING COMPRISING A CLAY HAVING THE CLAY CHARACTERISTICS OF MISSISSIPPI M & D CLAY, IN AMOUNT SUFFICIENT TO DEPOSIT AT LEAST APPROXIMATELY 10 LBS. OF CLAY SOLIDS PER 1000 SQUARE FEET OF SURFACE TREATED, AND DECORATIVE PAINT COATING SUPERIMPOSED ON SAID PRIMING COATING. 